Grannis climate

Grannis Frost Dates and Growing Season

NOAA 1991-2020 normals for Dequeen, 21.7 km from Grannis, elevation 407 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dequeen. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around March 29 and the first fall freeze around November 5, a growing season of about 222 days.

Median at 36°F
last April 10, first October 28
Median at 32°F
last March 29, first November 5
Median at 28°F
last March 13, first November 17

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FApr 26Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31Mar 22
32°FApr 16Apr 10Apr 5Apr 2Mar 29Mar 24Mar 20Mar 14Mar 7
28°FApr 3Mar 28Mar 23Mar 18Mar 13Mar 9Mar 4Feb 28Feb 22
24°FMar 19Mar 12Mar 8Mar 3Feb 28Feb 24Feb 19Feb 12Jan 31
20°FMar 10Mar 2Feb 24Feb 18Feb 11Feb 4Jan 30Jan 23Jan 13
16°FFeb 26Feb 14Feb 7Feb 1Jan 28Jan 20Jan 14Jan 7Dec 29

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FOct 15Oct 19Oct 22Oct 25Oct 28Oct 31Nov 1Nov 5Nov 10
32°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 7Nov 12Nov 16Nov 22
28°FNov 1Nov 5Nov 8Nov 13Nov 17Nov 21Nov 25Dec 1Dec 6
24°FNov 8Nov 14Nov 21Nov 27Dec 1Dec 4Dec 9Dec 18Dec 27
20°FNov 25Dec 1Dec 8Dec 15Dec 21Dec 26Jan 1Jan 6Jan 17
16°FDec 8Dec 17Dec 24Dec 30Jan 2Jan 8Jan 14Jan 21Feb 1

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F222215210205199194189185178
32°F249240234228222218213207199
28°F274267261255250243237232223
24°F309298290283277271264257246
20°F346335327319310304295286273
16°F365365362352344335330319303

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
97% of years
16°F or colder
75% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
3,024
Cooling degree days, base 65°F
1,980
Growing degree days, base 40°F
8,287
Growing degree days, base 45°F
6,711
Growing degree days, base 50°F
5,290
Growing degree days, base 55°F
4,027
Growing degree days, base 60°F
2,923

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January719029
February542154
March3739172
April16441337
May31169603
June1373822
July0502967
August0502967
September9296736
October13677414
November4018140
December648148

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 21.7 km from Grannis. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00031948 (Dequeen). Public domain.